The invention relates to the field of constructing pre-cast concrete panel and joist assemblies used in the construction industry, and more particularly to the field of forming such assemblies off-site and subsequently transporting the completed assemblies to the construction site for use as exterior wall members. Specifically, the invention relates to the field of pre-cast wall panels with lateral bridging members to counter the effects of wind load and suction, and the method of constructing such assemblies.
In traditional construction practice, walls in buildings are constructed from masonry blocks or are poured directly into forms set on the floor slab and then tilted into place after hardening. Both these methods are time consuming and the latter method greatly interferes with other construction operations because the floor space is occupied during the forming phase. Furthermore, the walls must be made relatively thick to withstand the effects of wind load and suction.
To provide a better system, a method has been developed for pre-fabricating concrete slab and joist assemblies to be used as walls. A number of pre-cast concrete panel and joist assemblies can be made and transported to the construction site, ready for installation at the first opportunity. Since the assemblies are pre-cast, construction is not delayed to wait for the setting of the poured concrete. The assemblies are modular in the sense that a number of assemblies are placed in position by crane and then joined together to form a continuous wall assembly. Because the assemblies are combined concrete slabs and joists, the slab itself can be thinner than a standard slab, saving expense and weight without sacrificing strength. A standard wall slab made in the traditional manner without joists is much thicker and too massive to transport easily. As with all construction, it is desirable to reduce the number of steps required, use less materials and simplify the operations. The concrete panel and joist assemblies are easily transportable and can be erected on site using light-weight equipment.
While it is well known to form pre-cast concrete panel and joist assemblies for use as floors or other load bearing members, this type of construction has not been applied to walls. Pre-cast wall panels must take into consideration and account for wind effects not encountered in floor situations. With floor panels, load forces in the downward or weight bearing direction are the only forces encountered. With wall panels however, the effect of wind on the upright exterior walls means that either wind load or wind suction may be present. That is, a pre-cast wall panel must be able to withstand stresses in both directions--a compressive load toward the interior of the building and a tensile load or suction toward the exterior of the building. The interior chords of the joists will be in tension in the compressive load situation and in compression in the suction situation. The standard methods for forming pre-cast panels do not take these factors into consideration, and if panels made from such methods are used in exterior walls, can result in a construction not able to withstand the stresses caused by wind.
To overcome the problems outlined above, the method of the invention provides for constructing a pre-cast concrete panel and joist assembly able to withstand both compressive loads and suction. The method incorporates the step of adding bridging members to interconnect the joists and concrete panel, the bridging providing the necessary lateral stability to overcome the problems of the wind effects. The specific structure and design of the bridging members and joist enable quick, efficient construction, and the resulting concrete panel and joist assembly is distinct from previously known assemblies.
It is an object of this invention to provide a pre-cast concrete panel and joist assembly able to be used as a wall member, and to provide a method of pre-casting and constructing such assembly.
It is an object of the invention to provide a method of pre-casting and constructing concrete slab and joist assemblies with lateral bridging members which is simple in operation.
It is a further object of this invention to provide such a method where pre-constructed joists are attached to a pre-cast, hardened concrete panel and lateral bridging members are easily interlocked with the joists.
It is a further object of the invention to provide a pre-cast panel and joist assembly having interlocking lateral bridging members.
It is a further object of the invention to provide such an assembly where the joist does not require an exterior chord, so that the overall depth of the assembly is reduced.